U.S. patent number 9,335,548 [Application Number 13/972,782] was granted by the patent office on 2016-05-10 for head-wearable display with collimated light source and beam steering mechanism.
This patent grant is currently assigned to Google Inc.. The grantee listed for this patent is Google Inc.. Invention is credited to Ozan Cakmakci, Anurag Gupta.
United States Patent |
9,335,548 |
Cakmakci , et al. |
May 10, 2016 |
Head-wearable display with collimated light source and beam
steering mechanism
Abstract
A head-wearable display includes a collimated light source, a
beam steering mechanism, and a synchronization controller. The
collimated light source selectively emits collimated light. The
beam steering mechanism is optically coupled to receive the
collimated light and angularly scans the collimated light between
beam steering states that each redirect the collimate light to a
different angular direction along at least one angular dimension.
The beam steering mechanism is coupled to scan the collimated light
across an eyebox. The synchronization controller is coupled to the
collimated light source and the beam steering mechanism to
synchronize selective emission of the collimated light from the
collimated light source with the beam steering states of the beam
steering mechanism to repetitiously draw an image in the
eyebox.
Inventors: |
Cakmakci; Ozan (Sunnyvale,
CA), Gupta; Anurag (Los Gatos, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Google Inc. |
Mountain View |
CA |
US |
|
|
Assignee: |
Google Inc. (Mountain View,
CA)
|
Family
ID: |
55859940 |
Appl.
No.: |
13/972,782 |
Filed: |
August 21, 2013 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06F
3/017 (20130101); G02B 27/0172 (20130101); G06F
3/013 (20130101); G02B 26/005 (20130101); G02B
27/0093 (20130101) |
Current International
Class: |
G02B
27/01 (20060101); G02B 26/00 (20060101); G02B
27/00 (20060101); G02F 1/29 (20060101); G06F
3/01 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Cakmakci, Ozan et al., "Head-Worn Displays: A Review", Journal of
Display Technology, vol. 2, No. 3, IEEE, Sep. 2006, pp. 199-216.
cited by applicant .
Smith, N.R. et al., "Experimental Validation of >1 kHz
Electrowetting Modulation", University/Government/Industry
Micro/Nano Symposium, 2008, UGIM 2008, 17th Biennial, IEEE, pp.
11-14. cited by applicant .
McManamon, Paul F. et al., "A Review of Phased Array Steering for
Narrow-Band Electrooptical Systems", Invited Paper, Proceedings of
the IEEE, vol. 97, No. 6, Jun. 2009, pp. 1078-1096. cited by
applicant .
Gao Renxi et al., "The Composite Structure of Hologram and Optical
Waveguide", www.intechopen.com, Holography, Research and
Technologies, Published online Feb. 28, 2011, pp. 109-132. cited by
applicant .
Epson, "Moverio.TM. BT-100 Wearable Display", Model: V11H423020, 2
pages downloaded from Internet on Aug. 21, 2013,
<http://www.epson.com/cgi-in/Store/jsp/Product.do?sku=V11H423020#produ-
ct-info>. cited by applicant.
|
Primary Examiner: Cerullo; Liliana
Attorney, Agent or Firm: Blakely Sokoloff Taylor &
Zafman LLP
Claims
What is claimed is:
1. An apparatus for a head-wearable display, comprising: a
collimated light source coupled to selectively emit collimated
light, wherein the collimated light source comprises a pixelated
light source that generates a two-dimensional ("2D") array of
collimated light pixels; a beam steering mechanism optically
coupled to receive the collimated light as the 2D array of
collimated light pixels emitted from the collimated light source
and to angularly scan the 2D array of collimated light pixels
between beam steering states that each redirect the 2D array of
collimated light pixels to a different angular direction along at
least one angular dimension, wherein the beam steering mechanism
scans the 2D array of collimated light pixels across an eyebox,
wherein the beam steering mechanism bends the 2D array of
collimated light pixels by a same angle at a given time for all
collimated light pixels output from the collimated light source at
the given time; and a synchronization controller coupled to the
collimated light source and the beam steering mechanism to
synchronize selective emission of the collimated light from the
collimated light source with the beam steering states of the beam
steering mechanism to repetitiously draw an image in the
eyebox.
2. The apparatus of claim 1, wherein the beam steering mechanism is
coupled to angularly scan between beam steering states angularly
separated along two dimensions.
3. The apparatus of claim 2, wherein the beam steering mechanism is
coupled to raster scan through the steering states angularly
separated along the two dimensions under the influence of the
synchronization controller.
4. The apparatus of claim 1, further comprising: an eye tracking
camera positioned to capture an eye image of an eye within the
eyebox, wherein the synchronization controller is coupled to the
eye tracking camera to determine a gazing direction based upon the
eye image and to selectively enable the collimated light pixels
only within a localized subset of the pixelated light source based
upon the determined gazing direction, wherein the localized subset
is less than all of the collimated light pixels within the
pixelated light source.
5. The apparatus of claim 4, wherein the beam steering mechanism
comprises a two-dimensional array of beam steering elements and
wherein a subset of the beam steering elements localized about the
gazing direction are enabled by the synchronization controller to
angularly steer the collimated light pixels while the beam steering
elements outside of the subset of the beam steering elements are
disabled and do not angularly scan passing light.
6. The apparatus of claim 1, wherein the beam steering mechanism
comprises: a first layer having a first two-dimensional ("2D")
array of electrowetting prisms coupled to beam steer along a first
angular axis; and a second layer having a second 2D array of
electrowetting prisms coupled to beam steer along a second angular
axis orthogonal to the first angular axis.
7. The apparatus of claim 1, wherein the beam steering mechanism
comprises a liquid crystal polarization grating.
8. The apparatus of claim 1, wherein the collimated light source
and the beam steering mechanism are see-through such that a user
can view ambient scene light through the collimated light source
and the beam steering mechanism.
9. The apparatus of claim 1, wherein the collimated light source
comprises: a collimator including a two-dimensional ("2D") array of
micro-mirrors; and a light source module including a 2D array of
divergent light sources each optically aligned with a corresponding
one of the micro-mirrors, wherein the light source module is
disposed between the collimator and the beam steering mechanism
such that divergent light emitted from the light source module
towards the collimator is reflected back towards the beam steering
mechanism through the light source module as collimated light
pixels.
10. The apparatus of claim 1, wherein the collimated light source
comprises: a collimator including a two-dimensional ("2D") array of
transmissive micro-lenses; and a light source module including a 2D
array of divergent light sources each optically aligned with a
corresponding one of the micro-mirrors, wherein the collimator is
disposed between the light source module and the beam steering
mechanism such that divergent light emitted from the light source
module is collimated upon passing through the collimator to form
collimated light pixels.
11. The apparatus of claim 1, wherein the collimated light source
comprises: a divergent light source coupled to generate divergent
light; a collimating lens positioned to collimate the divergent
light into the collimated light; a lightguide for guiding the
collimated light received from the collimating lens; and one or
more emission pixels disposed along a surface of the lightguide,
wherein the one or more emission pixels are coupled to the
synchronization controller to selectively emit the collimated light
in synch with the angularly scanning of the beam steering mechanism
under the influence of the synchronization controller to draw the
image in the eyebox.
12. The apparatus of claim 11, wherein the one or more emission
pixels comprise one or more switchable Bragg gratings configured to
selectively emit the collimated light from the lightguide along a
direction that is substantially normal to the surface of the
lightguide.
13. The apparatus of claim 12, wherein the lightguide comprises a
planar lightguide, and wherein the head-wearable display further
comprises: a linear array of divergent light sources; a linear
array of collimating lenses; and a two-dimensional array of
emission pixels disposed along the surface of the planar
lightguide.
14. The apparatus of claim 1, wherein the collimated light source
comprises: a two-dimensional ("2D") pixelated array of divergent
light sources; and a collimator disposed in an optical path between
the two-dimensional pixelated array of divergent light sources and
the beam steering mechanism.
15. The apparatus of claim 14, wherein the collimator comprises one
of a 2D array of micro-lenses or photonic crystals implementing a
super-collimation effect.
16. A method of operation of a head-worn display, comprising:
selectively emitting collimated light as a two-dimensional ("2D")
array of collimated light pixels; directing the 2D array of
collimated light pixels through a beam steering mechanism
positioned in front of an eye of a user; angularly scanning the 2D
array of collimated light pixels into an eyebox, wherein the 2D
array of collimated light pixels is angularly scanned across beam
steering states angularly separated along two dimensions, wherein
the 2D array of collimated light pixels are bent by a same angle at
a given time for all collimated light pixels output from the
collimated light source at the given time when angularly scanned
across the beam steering states; and synchronizing the selective
emission of the collimated light with the angular scanning of the
collimated light to repetitiously draw the image in the eyebox.
17. The method of claim 16, wherein the collimated light is
sequentially raster scanned between the beam steering states such
that all the collimated light emitted during a given beam steering
state is redirected by a common angle and each beam steering state
is associated with a different angle.
18. The method of claim 17, further comprising: capturing an eye
image of an eye within the eyebox; determining a gazing direction
based upon the eye image; and selectively enabling the collimated
light pixels only within a localized subset of the collimated light
pixels based upon the determined gazing direction, wherein the
localized subset is less than all of the collimated light
pixels.
19. The method of claim 18, further comprising: enabling a subset
of the beam steering elements within the beam steering mechanism
localized about the gazing direction to angularly steer the
collimated light pixels; and disabling the beam steering elements
outside of the subset of the beam steering elements such that those
beam steering elements do not angularly scan ambient light.
20. A head-wearable display, comprising: a see-through display
including: a collimated light source coupled to selectively emit
collimated light as a two-dimensional ("2D") array of collimated
light pixels; a beam steering mechanism optically coupled to
receive the 2D array of collimated light pixels emitted from the
collimated light source and to angularly scan the 2D array of
collimated light pixels between beam steering states that each
redirect the 2D array of collimated light pixels to a different
angular direction spread across two angular dimensions, wherein the
beam steering mechanism scans the 2D array of collimated light
pixels across an eyebox, wherein the beam steering mechanism bends
the 2D array of collimated light pixels by a same angle at a given
time for all collimated light pixels output from the collimated
light source at the given time; and a synchronization controller
coupled to the collimated light source and the beam steering
mechanism to synchronize selective emission of the collimated light
from the collimated light source with the beam steering states of
the beam steering mechanism to repetitiously draw an image in the
eyebox; and a frame assembly to support the see-through display for
wearing on a head of a user with the beam steering mechanism
positioned in front of and facing an eye of the user.
21. The head-wearable display of claim 20, wherein the collimated
light source comprises a pixelated light source that generates the
two-dimensional ("2D") array of collimated light pixels.
22. The head-wearable display of claim 21, further comprising: an
eye tracking camera positioned to capture an eye image of an eye
within the eyebox, wherein the synchronization controller is
coupled to the eye tracking camera to determine a gazing direction
based upon the eye image and to selectively enable the collimated
light pixels only within a localized subset of the pixelated light
source based upon the determined gazing direction, wherein the
localized subset is less than all of the collimated light pixels
within the pixelated light source.
23. The head-wearable display of claim 20, wherein the collimated
light source comprises: a collimator including a two-dimensional
("2D") array of micro-mirrors; and a light source module including
a 2D array of divergent light sources each optically aligned with a
corresponding one of the micro-mirrors, wherein the light source
module is disposed between the collimator and the beam steering
mechanism such that divergent light emitted from the light source
module towards the collimator is reflected back towards the beam
steering mechanism through the light source module as collimated
light pixels.
24. The head-wearable display of claim 20, wherein the collimated
light source comprises: a collimator including a two-dimensional
("2D") array of transmissive micro-lenses; and a light source
module including a 2D array of divergent light sources each
optically aligned with a corresponding one of the micro-lenses,
wherein the collimator is disposed between the light source module
and the beam steering mechanism such that divergent light emitted
from the light source module is collimated upon passing through the
collimator to form collimated light pixels.
25. The head-wearable display of claim 20, wherein the collimated
light source comprises: a divergent light source coupled to
generate divergent light; a collimating lens positioned to
collimate the divergent light into the collimated light; a
lightguide for guiding the collimated light received from the
collimating lens; and one or more emission pixels disposed along a
surface of the lightguide, wherein the one or more emission pixels
are coupled to the synchronization controller to selectively emit
the collimated light in synch with the angularly scanning of the
beam steering mechanism under the influence of the synchronization
controller to draw the image in the eyebox.
26. An apparatus for a head-wearable display, comprising: a
collimated light source coupled to selectively emit collimated
light, wherein the collimated light source comprises a pixelated
light source that generates a two-dimensional ("2D") array of
collimated light pixels; a beam steering mechanism optically
coupled to receive the collimated light as the 2D array of
collimated light pixels emitted from the collimated light source
and to angularly scan the 2D array of collimated light pixels
between beam steering states that each redirect the 2D array of
collimated light pixels to a different angular direction along at
least one angular dimension, wherein the beam steering mechanism
scans the 2D array of collimated light pixels across an eyebox; a
synchronization controller coupled to the collimated light source
and the beam steering mechanism to synchronize selective emission
of the collimated light from the collimated light source with the
beam steering states of the beam steering mechanism to
repetitiously draw an image in the eyebox; and an eye tracking
camera positioned to capture an eye image of an eye within the
eyebox, wherein the synchronization controller is coupled to the
eye tracking camera to determine a gazing direction based upon the
eye image and to selectively enable the collimated light pixels
only within a localized subset of the pixelated light source based
upon the determined gazing direction, wherein the localized subset
is less than all of the collimated light pixels within the
pixelated light source.
27. A method of operation of a head-worn display, comprising:
selectively emitting collimated light as a two-dimensional ("2D")
array of collimated light pixels; directing the 2D array of
collimated light pixels through a beam steering mechanism
positioned in front of an eye of a user; angularly scanning the 2D
array of collimated light pixels into an eyebox, wherein the 2D
array of collimated light pixels is angularly scanned across beam
steering states angularly separated along two dimensions;
synchronizing the selective emission of the collimated light with
the angular scanning of the collimated light to repetitiously draw
an image in the eyebox; capturing an eye image of an eye within the
eyebox; determining a gazing direction based upon the eye image;
and selectively enabling the collimated light pixels only within a
localized subset of the collimated light pixels based upon the
determined gazing direction, wherein the localized subset is less
than all of the collimated light pixels.
Description
TECHNICAL FIELD
This disclosure relates generally to the field of optics, and in
particular but not exclusively, relates to head-wearable
displays.
BACKGROUND INFORMATION
A head-wearable or head-mounted display ("HMD") is a display device
worn on or about the head. HMDs usually incorporate some sort of
near-to-eye optical system to display an image within a few
centimeters of the human eye. Single eye displays are referred to
as monocular HMDs while dual eye displays are referred to as
binocular HMDs. Some HMDs display only a computer generated image
("CGI"), while other types of HMDs are capable of superimposing a
computer generated image ("CGI") over a real-world view. This
latter type of HMD is often referred to as augmented reality
because the viewer's image of the world is augmented with an
overlaying CGI, also referred to as a heads-up display ("HUD").
One goal of designing HMDs is to have the device disappear from an
observer point of view. Conventional HMDs are implemented with a
light source that emits display light initially having a cone of
divergence. In order to bring this display light into focus in a
near-to-eye configuration, optics are used to collimate or nearly
collimate this divergent light. These optics are typically
implemented using one or more reflective, refractive, or
diffractive lenses. These conventional optical elements typically
must tradeoff bulk and size with field of view, eyebox, and
spectral bandwidth.
HMDs have numerous practical and leisure applications. Aerospace
applications permit a pilot to see vital flight control information
without taking their eye off the flight path. Public safety
applications include tactical displays of maps and thermal imaging.
Other application fields include video games, transportation, and
telecommunications. Due to the infancy of this technology, there is
certain to be new found practical and leisure applications as the
technology evolves; however, many of these applications are limited
due to the cost, size, field of view, and efficiency of
conventional optical systems used to implement existing HMDs.
BRIEF DESCRIPTION OF THE DRAWINGS
Non-limiting and non-exhaustive embodiments of the invention are
described with reference to the following figures, wherein like
reference numerals refer to like parts throughout the various views
unless otherwise specified. The drawings are not necessarily to
scale, emphasis instead being placed upon illustrating the
principles being described.
FIG. 1 is a functional block diagram illustrating a head-wearable
display system with a collimated light source synchronized to a
beam steering mechanism, in accordance with an embodiment of the
disclosure.
FIGS. 2A-C illustrate plan views of different emission patterns of
collimated light that can be emitted by a collimated light source,
in accordance with embodiments of the disclosure.
FIGS. 3A-3D illustrate how a beam steering mechanism operates to
scan collimated light between beam steering states that each
redirect the collimated light to a different angular direction, in
accordance with an embodiment of the disclosure.
FIG. 4 is a flow chart illustrating a process of operation of the
head-wearable display system, in accordance with an embodiment of
the disclosure.
FIG. 5 illustrates a beam steering mechanism implemented using
two-dimensional arrays of controllable beam steering prisms, in
accordance with an embodiment of the disclosure.
FIGS. 6A-B illustrate a head-wearable display system implemented
with a mirror based collimator, in accordance with an embodiment of
the disclosure.
FIGS. 7A-B illustrate a head-wearable display system implemented
with a micro-lens array based collimator, in accordance with an
embodiment of the disclosure.
FIGS. 8A-B illustrate a head-wearable display system implemented
with a planar lightguide, in accordance with an embodiment of the
disclosure.
FIG. 9 is a top view illustration of a binocular head wearable
display using two see-through displays that each include a
collimated light source synchronized to a beam steering mechanism,
in accordance with an embodiment of the disclosure.
DETAILED DESCRIPTION
Embodiments of a system, apparatus, and method of operation for
head-wearable display implemented with beam steering are described
herein. In the following description numerous specific details are
set forth to provide a thorough understanding of the embodiments.
One skilled in the relevant art will recognize, however, that the
techniques described herein can be practiced without one or more of
the specific details, or with other methods, components, materials,
etc. In other instances, well-known structures, materials, or
operations are not shown or described in detail to avoid obscuring
certain aspects.
Reference throughout this specification to "one embodiment" or "an
embodiment" means that a particular feature, structure, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the present invention. Thus,
the appearances of the phrases "in one embodiment" or "in an
embodiment" in various places throughout this specification are not
necessarily all referring to the same embodiment. Furthermore, the
particular features, structures, or characteristics may be combined
in any suitable manner in one or more embodiments.
FIG. 1 is a functional block diagram illustrating a system 100 for
implementing a head-wearable display with a collimated light source
synchronized to a beam steering mechanism, in accordance with an
embodiment of the disclosure. The illustrated embodiment of system
100 includes a collimated light source 105, a beam steering
mechanism 110, a synchronization controller 115, and an optional
eye tracking camera 120.
System 100 operates to repetitiously draw an image into an eyebox
125 to be aligned with an eye 130. The image is drawn by
synchronizing the emission of collimated light 135 from collimated
light source 105 with the beam steering induced by beam steering
mechanism 110. Beam steering mechanism 110 repetitiously scans
through beam steering states (e.g., S1, S2, S3 . . . ) that each
direct collimated light 135 towards a different angular direction
while maintaining the collimated nature of collimated light 135
that reaches eye 130.
All collimated light that reaches eye 130 from a given angle is
focused by eye 130 to a point and thus represents a given point or
pixel within an image. By pulsing collimated light source 105 on
and off in synchronization with the currently selected beam
steering state of beam steering mechanism 110 an image can be drawn
into eyebox 125 with a field of view (e.g., eight degrees). When
this image is repetitiously redrawn, eye 130 will perceive a
substantially constant image. The image can be updated and changed
by changing the on/off synchronization between collimated light
source 105 and beam steering mechanism 110. In one embodiment,
synchronization controller 115 is a microcontroller coupled to
control collimated light source 105 and beam steering mechanism 110
according to executable instructions (e.g., software/firmware
instructions).
In one embodiment, synchronization controller 115 is further
coupled to an eye tracking camera 120 to determine the gazing
direction of eye 130 and increase the field of view ("FOV") of
system 100. This gaze tracking mechanism is described in greater
detail below in connection with FIG. 4.
Collimated light source 105 may be implemented in a variety of
different manners. For example, collimated light source 105 may be
implemented using one or more divergent light sources (e.g., LEDs,
OLEDs, lasers, or otherwise) that are collimated with optics (e.g.,
refractive, reflective, or diffractive lens elements), if
necessary. The divergent light source may be directly switched on
and off or external optical elements used to modulate the emitted
light.
FIGS. 2A-C illustrate plan views of different emission patterns of
collimated light 135 that can be emitted by different
configurations of collimated light source 105. The embodiment of
FIG. 2A illustrates how collimated light source 105 can be designed
to emit a single large beam of collimated light 205. The embodiment
of FIG. 2B illustrates how collimated light source 105 can be
designed to emit rows (or columns) of collimated light 210. The
embodiment of FIG. 2C illustrates how collimated light source 105
can be designed as a pixelated collimated light source that emits a
2D array of collimated light pixels 215. These emission patterns
for collimated light 135 are directed into beam steering mechanism
110, which then directs the collimated light 135 at selectable
angles (beam steering states) into eyebox 125 in a repetitious
manner under the influence of synchronization controller 115.
FIGS. 3A-3C illustrate how beam steering mechanism 110 operates to
scan collimated light 135 between beam steering states that each
redirect the collimated light 135 to a different angular direction,
in accordance with an embodiment of the disclosure. FIGS. 3A and 3B
illustrate how, in one embodiment, beam steering mechanism 110 can
redirect the collimated light 135 in different directions along two
orthogonal angular dimensions (e.g., x and y). Each angular
direction corresponds to a different beam steering state. However,
in each beam steering state, all collimated light 135 that is
passed through beam steering mechanism 110 is redirected by the
same angle to preserve the collimated characteristic of the light
reaching eye 130 within eyebox 125. FIG. 3C illustrates how
synchronization controller 115 manipulates beam steering mechanism
110 to raster scan through the beam steering states (i.e., S1 to
Sxy). This raster scan pattern has the effect of scanning the
collimated light 135 over eyebox 125 by sequentially cycling
through the beam steering states. By quickly repeating the raster
scan pattern illustrated in FIG. 3C, a constant image is perceived
by eye 130.
FIG. 4 is a flow chart illustrating a process 400 of operation of
system 100 including the optional eye tracking feature, in
accordance with an embodiment of the disclosure. The order in which
some or all of the process blocks appear in process 400 should not
be deemed limiting. Rather, one of ordinary skill in the art having
the benefit of the present disclosure will understand that some of
the process blocks may be executed in a variety of orders not
illustrated, or even in parallel. Process 400 is described with
reference to FIGS. 1, 2C, and 3D. FIG. 2C illustrates a planar view
along the z-axis of a pixelated implementation of collimated light
source 105. FIG. 3D is a planar view along the z-axis of a
pixelated implementation of beam steering mechanism 110.
In a process block 405, the gazing direction of eye 130 is
determined. The gazing direction is determined using eye tracking
camera 120 to capture an image of eye 130. Eye tracking camera 120
may be implemented using a complementary metal-oxide-semiconductor
("CMOS") image sensor or charged coupled device ("CCD") image
sensor that is mounted in a position to have a constant view of eye
130. The eye image is then analyzed by synchronization controller
115 to determine the direction in which eye 130 is gazing. In one
embodiment, gazing direction may be calculated based upon the
position of the iris in the captured image.
When collimated light source 105 is implemented as a pixelated
collimated light source (illustrated in FIG. 2C), determining the
gazing direction can be used to dynamically translate eyebox 125 in
real-time to effectively increase the FOV of system 100. Returning
to FIG. 4, once the gazing direction has been determined,
collimated light pixels 215 within a localized subset 220
surrounding gazing direction 225 are enabled while collimated light
pixels 215 outside of localized subset 220 are disabled (process
block 410). Thus, collimated light pixels 215 within localized
subset 220 are synchronously enabled to selectively emit light
under the control of synchronization controller 115 while
collimated light pixels 215 outside of localized subset 220 are
disabled and do not emit light.
Similarly, referring to FIG. 3D, a localized subset 320 of beam
steering elements 315 within beam steering mechanism 110 are also
enabled while beam steering elements 315 outside of localized
subset 320 are disabled (process block 415). The localized subset
320 of beam steering elements 315 are those elements that are
optically aligned with collimated light pixels 215 within localized
subset 220. Enabling beam steering elements 315 within localized
subset 320 means these localized beam steering elements are
operated to repetitiously scan through the beam steering states
(e.g., S1 through Sxy). Correspondingly, disabling beam steering
elements 315 outside the localized subset 320 means those elements
are set to a fixed beam steering state so as not to angularly scan
passing light through a sequence of angularly distinct directions.
In one embodiment, disabling beam steering elements 315 sets them
to a beam steering state that does not alter the direction of
incident light. Thus, in an embodiment where beam steering
mechanism 110 and collimated light source 105 are transmissive
elements in a see-through display, ambient scene light can pass
through these elements outside of localized subsets 220 and 320
without being washed out by collimated light 135 or distorted by
beam steering mechanism 110.
In a process block 415, beam steering elements 315 within localized
subset 320 repetitiously scan through the beam steering states
(e.g., S1 through Sxy). This scanning sequentially redirects
collimated light 135 through the sequence of angularly distinct
directions provided by beam steering states S1 through Sxy.
If the user's gazing direction remains stationary (decision block
425), then the image continues to be raster scanned across eyebox
125 in process block 420. However, if the user's gazing direction
changes (decision block 425), then process 400 loops back to
process block 405 where the gazing direction is again
re-determined. Thus, synchronization controller 115 controls
collimated light source 105 and beam steering mechanism 110 to
translate localized subsets 220 and 320 to follow the gazing
direction of the user in real-time based upon feedback from eye
tracking camera 120 thereby increasing the dynamic FOV of system
100.
Process 400 describes operation of display system 100 using eye
tracking with localized beam steering and pixel light emission.
However, other embodiments of system 100 may be implemented without
eye tracking and without constraining the beam steering and/or
pixel light emission to localized areas surrounding the gazing
direction 225.
FIG. 5 illustrates a beam steering mechanism 500 implemented using
two layers of 2D arrays of controllable beam steering prisms, in
accordance with an embodiment of the disclosure. Beam steering
mechanism 500 is one possible implementation of beam steering
mechanism 110. The illustrated embodiment of beam steering
mechanism 500 includes a vertical beam steering layer 505 and a
horizontal beam steering layer 510. Each beam steering layer 505 or
510 includes a 2D array of beam steering elements 515.
Each beam steering element 515 operates as an adjustable prism that
can independently bend collimated light 135 incident on its ambient
facing side to a selectable angle on its eye-ward facing side. In
one embodiment, beam steering elements 515 are implemented using
electrowetting micro-prisms. Electrowetting micro-prisms include an
oil filled cavity surrounded on either side by electrostatic plates
that can manipulate the shape of the oil in the cavity thereby
creating an adjustable prism. Electrowetting micro-prisms have been
found to be capable of implementing a beam steering raster in
excess of 1 kHz, which is in a range that is adequate to implement
beam steering mechanism 110. In the illustrated embodiment, two
layers of beam steering elements 515 are used to achieve beam
steering in two orthogonal angular directions. Thus, vertical beam
steering layer 505 includes prisms that can be manipulated under
control of synchronization controller 115 to bend collimated light
135 along a vertical angular axis and horizontal beam steering
layers 510 includes prisms that can be manipulated under control of
synchronization controller 115 to bend collimated light 135 along a
horizontal angular axis.
In one embodiment, it has been calculated that a steering response
frequency of 2.765 kHz is adequate to operate beam steering
mechanism 500 having 276 independent beam steering states. Of
course, other steering frequencies and number of steering states
may be implemented. If it is desired to arrange the beam steering
states into a field of view ("FOV") having a 4:3 ratio, then 276
beam steering states roughly provides 19 x-axis steering states and
14 y-axis steering states. A derivation of why 276 beam steering
states is deemed to be adequate follows below.
The human eye has an angular resolution of approximately 1 arcmin,
(below which it cannot discern angular separations), a FOV of
approximately 2 degrees at any given moment (without moving the
eye), and a response rate of about 30 Hz. Accordingly, a display
that provides 18 to 20 arcmin angular resolution, 8 degrees of
instantaneous diagonal FOV, and a refresh rate of 10 Hz can be
deemed acceptable for certain uses. An angular resolution of 18 to
20 arcmin is selected as a value that provides adequate angular
resolution while not resulting in display features that are so
small that diffraction unduly compromises the image. With these
assumptions, a 4:3 ratio image has: xFOV=6.4 degrees, and yFOV=4.8
degrees. For an eye relief (dimension ER in FIG. 1) of 18 mm and an
eyebox diameter (dimension ED in FIG. 1) of 8 mm, the dimensions of
the beam steering device are: Lx=2*tan(xFOV)*ER+ED=12.038 mm, and
Ly=2*tan(yFOV)*ER+ED=11.023 mm. This results in the following
number of beam steering states:
.times..times..times. ##EQU00001## ##EQU00001.2##
It should be appreciated that other mechanisms may be used to
implement beam steering mechanism 110. For example, in another
embodiment, beam steering mechanism 110 may be implemented using a
liquid crystal polarization grating. Furthermore, beam steering
mechanism 110 need not be implemented as a pixelated structure, but
rather may be implemented as a single continuous structure since
all collimated light 135 is bent in the same direction by the same
angle at a given time. However, a non-pixelated embodiment may
require additional optical elements to counter-act beam steering
for a see-through display.
FIG. 6A illustrates a head-wearable display system 600 implemented
with a mirror based collimator, in accordance with an embodiment of
the disclosure. System 600 is one possible implementation of system
100 illustrated in FIG. 1. The illustrated embodiment of system 600
includes beam steering mechanism 110, a collimated light source
605, synchronization controller 115, and optionally eye tracking
camera 120. The illustrated embodiment of collimated light source
605 includes a light source module 607 and a collimator 609.
Collimated light source 605 is a pixelated light source that
generates collimated light pixels 135. Light source module 607
includes a 2D array of divergent light sources 620 (e.g., LEDs,
OLED, quantum dots, etc.), which are each aligned with a
corresponding micro-mirror 625 within collimator 609. In one
embodiment, each divergent light source 620 is positioned at the
focal point of a corresponding micro-mirror 625.
The divergent light emitted by a given divergent light source 620
is reflected and collimated by a corresponding micro-mirror 625 of
collimator 609. The reflected and collimated light is directed back
towards beam steering mechanism 110 as collimated light 135. Thus,
collimated light source 605 is a 2D pixelated light source. FIG. 6B
illustrates a plan view of light source module 607.
FIG. 7A illustrates a head-wearable display system 700 implemented
with a micro-lens array based collimator, in accordance with an
embodiment of the disclosure. System 700 is one possible
implementation of system 100 illustrated in FIG. 1. The illustrated
embodiment of system 700 includes beam steering mechanism 110, a
collimated light source 705, synchronization controller 115, and
optionally eye tracking camera 120. The illustrated embodiment of
collimated light source 705 includes a light source module 707 and
a collimator 709.
Collimated light source 705 is a pixelated light source that
generates collimated light pixels 135. Light source module 707
includes a 2D array of divergent light sources 720 (e.g., LEDs,
OLED, quantum dots, etc.), which are each aligned with a
corresponding micro-lens 725 within collimator 709. In one
embodiment, each divergent light source 720 is positioned at the
focal point of a corresponding micro-lens 725.
The divergent light emitted by a given divergent light source 720
is directed to and collimated by a corresponding micro-lens 725 and
output as collimated light 135. Thus, collimated light source 705
is a 2D pixelated light source. FIG. 7B illustrates a plan view of
light source module 707.
FIG. 8A illustrates a head-wearable display system 800 implemented
with a planar lightguide, in accordance with an embodiment of the
disclosure. System 800 is one possible implementation of system 100
illustrated in FIG. 1. The illustrated embodiment of system 800
includes beam steering mechanism 110, a collimated light source
805, synchronization controller 115, and optionally eye tracking
camera 120. The illustrated embodiment of collimated light source
805 includes a divergent light source 810, a collimating lens 815,
a planar lightguide 820, and emission pixels 825.
During operation, divergent light source 810 (e.g., LED, quantum
dot, etc.) emits divergent light into collimating lens 815, which
collimates the light before entering into planar lightguide 820.
The collimated light is guided within planar lightguide 820 via
total internal reflection, expanding the collimated light beam out
along its length. In one embodiment, emission pixels 825 are
switchable Bragg gratings ("SBG") that are operated under the
influence of synchronization controller 115. SBG can be operated to
either maintain the TIR characteristic of planar lightguide 820 so
that the collimated light continues to propagate within the
lightguide, or defeats the TIR condition permitting the collimated
light to selectively escape as collimated light 135 along a
designed trajectory. In one embodiment, the trajectory may be
designed to be substantially normal to the emission surface of
planar lightguide 820.
FIG. 8B illustrates a plan view of planar lightguide 820 including
a 2D array of emission pixels 825, in accordance with an embodiment
of the disclosure. In this 2D pixelated embodiment, a linear array
of divergent light sources 810 and collimating lenses 815 may line
the side of planar lightguide 820. Of course, emission pixels 825
may be disposed over the emission side of planar lightguide 820
using a variety of other patterns. For example, emission pixels 825
can be sized and oriented to implement any of the emission patterns
illustrated in FIG. 2A, 2B, or 2C. Although FIG. 8B illustrates an
array of divergent light sources 810 and collimating lenses 815,
other embodiments may use a single light source and a single
collimator to inject light into planar lightguide 820.
FIG. 9 is a top view illustration of a binocular head wearable
display 900 using two see-through displays 901 that each include a
collimated light source synchronized to a beam steering mechanism,
in accordance with an embodiment of the disclosure. Each
see-through display 901 may be implemented with various embodiments
or combinations of systems 100, 600, 700, or 800 as discussed
herein. The see-through displays 900 are mounted to a frame
assembly, which includes a nose bridge 905, left ear arm 910, and
right ear arm 915. Although FIG. 9 illustrates a binocular
embodiment, display 900 may also be implemented as a monocular
display.
The see-through displays 901 are secured into an eye glass
arrangement or head wearable display that can be worn on the head
of a user. The left and right ear arms 910 and 915 rest over the
user's ears while nose bridge 905 rests over the user's nose. The
frame assembly is shaped and sized to position each display in
front of a corresponding eye 125 of the user. Other frame
assemblies having other shapes may be used (e.g., a visor with ear
arms and a nose bridge support, a single contiguous headset member,
a headband, goggles type eyewear, etc.).
The illustrated embodiment of display 900 is capable of displaying
an augmented reality to the user. Each see-through display 901
permits the user to see a real world image via external scene light
902. Left and right (binocular embodiment) image light (collimated
light 135) is generated by collimated light source 105 and scanned
across the user's eye 130 via beam steering mechanism 110. The
image light is seen by the user as a virtual image in front of or
superimposed over external scene light 902. In some embodiments,
external scene light 902 may be fully, partially, or selectively
blocked to provide sun shading characteristics and increase the
contrast of the image light.
The processes explained above may be described in terms of computer
software and hardware. The techniques described may constitute
machine-executable instructions embodied within a tangible or
non-transitory machine (e.g., computer) readable storage medium,
that when executed by a machine will cause the machine to perform
the operations described. Additionally, the processes may be
embodied within hardware, such as an application specific
integrated circuit ("ASIC") or otherwise.
A tangible machine-readable storage medium includes any mechanism
that provides (i.e., stores) information in a form accessible by a
machine (e.g., a computer, network device, personal digital
assistant, manufacturing tool, any device with a set of one or more
processors, etc.). For example, a machine-readable storage medium
includes recordable/non-recordable media (e.g., read only memory
(ROM), random access memory (RAM), magnetic disk storage media,
optical storage media, flash memory devices, etc.).
The above description of illustrated embodiments of the invention,
including what is described in the Abstract, is not intended to be
exhaustive or to limit the invention to the precise forms
disclosed. While specific embodiments of, and examples for, the
invention are described herein for illustrative purposes, various
modifications are possible within the scope of the invention, as
those skilled in the relevant art will recognize.
These modifications can be made to the invention in light of the
above detailed description. The terms used in the following claims
should not be construed to limit the invention to the specific
embodiments disclosed in the specification. Rather, the scope of
the invention is to be determined entirely by the following claims,
which are to be construed in accordance with established doctrines
of claim interpretation.
* * * * *
References